The present invention relates to a quantitative competition system and method which compare aimed or intended values of participants and publish the highest or lowest value but hide the other values, and a recording medium on which there is recorded a program for implementing the method. More particularly, the invention pertains to a system and method for quantitative comparison of secret values, for example, in electronic lottery, electronic voting, or electronic sealed-bid auction under circumstances where many participants are allowed to access the server online across the Internet.
FIG. 1 is depicts in block form the configuration of a conventional electronic competitive bidding or sealed-bid auction system. A notice of auction is input to bidding devices 101 to 10M, which send their identifiers ID1 to IDM and bidding prices PR1 to PRM to a bid-opening device 20. In this transfer of each data, if it is desirable to keep the data secret, the bidding price is sent in compressed form, and if it is necessary to identify the data, it is sent together with a digital signature of the bidder. The bid-opening device 20 detects the highest (or lowest) one of the bid values received from the bidding devices 101 to 10M, and outputs the winning bid and the identifier corresponding thereto. This scheme is disclosed, for example, in Japanese Patent Application Laid-Open Gazette No. 118876/90 entitled “Electronic Bidding System.” On the other hand, schemes which publish only the winning bid but hide other information involved are disclosed, for example, in Kazuo SAKO, “Auction Protocol Which Hides Bids of Losers,” The Symposium on Cryptography and Information Security, SCIS'99, and in Shingo MIYAZAKI and Kouichi SAKURAI, “A Bulletin-Board Base Digital Auction Scheme with Bidding Down Strategy,” The Symposium on Cryptography and Information Security SCIS'99.
The sealed-bid auction scheme to which the present invention is applied satisfies the requirements mentioned below.
*Only bidding prices are used to determine the winning bid; that is, the successful bidding device is not determined using other information.
The bid-opening device and a provisional identifier registration device neither cheat nor malfunction.